JPS63159826A - Driving method for liquid crystal display element - Google Patents

Abstract

PURPOSE:To simplify a power source circuit by supplying a necessary pulse train to common electrodes and segment electrodes, respectively, which are opposed by inserting a liquid crystal between them and constitute two liquid crystal display elements, respectively. CONSTITUTION:Common electrodes C1-C3 and segment electrodes S1-S4 constitute two liquid crystal elements, respectively. A first pulse train E1 of a driving pulse of pulse width (t) and a high frequency pulse of the same voltage as that of a driving pulse generated during the time (t) before or after said pulse, and a second pulse train E2 which has inverted a level of the pulse train E1 are supplied to the electrode C1. To the other electrode C2, a pulse train whose phase is shifted by the time (t) from the electrode C1 is supplied. On the other hand, pulse trains P3-P6 which consist of a pulse train the same in voltage as that of driving pulses of the electrodes C1, C2, a period of the time 4t and a duty of 1/2, and whose phases are shifted by 1/4 period each are supplied selectively to the electrodes S1-S4. By using this same voltage, a voltage raising circuit and a voltage lowering circuit become unnecessary, and the constitution of a power source circuit is simplified. Also, an external capacitor is also unnecessary, and a chip area of an integrated circuit becomes small.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a method for driving a liquid crystal display element.

[Prior Art] Conventionally, for example, a display of a digital watch, etc., has been made by placing segment electrodes S-S4 in FIG. 3 facing common electrodes C1 to C3 as shown in FIG. Seven liquid crystal display elements A-Ar are formed horizontally.

The liquid crystal display element is driven as follows. For example, when driving the liquid crystal display elements A 1 and A 2 , the common electrodes C and C shown in FIG. 2 are constantly supplied with the pulse P1°P shown in FIG. 5, respectively. On the other hand, selection pulse trains P3 to P6 whose phases are shifted by 1/4 period are selectively supplied to the segment electrode S1.

Voltages 1 and V2 are applied to the liquid crystal display elements A and A2 by the pulse P, respectively, and both become non-displaying. The pulse train P4 causes the liquid crystal display elements A and A to
Voltages V and ■ are applied to these, respectively, to display and non-display, respectively. Furthermore, voltages v and 2 are applied to the liquid crystal display elements A and A2, respectively, by the pulse train P, and both are displayed. Furthermore, voltages v 1 and V 8 are applied to the liquid crystal display elements A 1 and A 2 by the pulse train P 6 , so that they become non-display and display, respectively.

As described above, the liquid crystal display elements A and A2 are selectively displayed.

[Problems to be Solved by the Invention] In the above driving method, the pulses supplied to the common electrode require two types of potential, which requires a step-up circuit or a step-down circuit. It was necessary to connect an external capacitor. As a result, the power supply circuit has become complicated, which has been an impediment to cost reduction.

The present invention aims at simplifying a power supply circuit.

[Means for Solving the Problems] The present invention provides first and second pulse trains each consisting of a drive pulse with a pulse width t and a high-frequency pulse with the same voltage as the drive pulse, on one of the two common electrodes. The other common electrode is supplied with the first and second pulse trains with different phases, and the segment electrodes are supplied with the same voltage as the drive pulse with a period of time 4t and a duty of 1.
/2 pulses, phase shifted by 1/4 period
By selectively supplying selected types of pulse trains,
The liquid crystal display element is configured to selectively display information.

[Example] In FIG. 1, a pulse train P and a pulse train P8 are constantly supplied to the common electrodes C and C, respectively. Pulse train P7
consists of a first pulse train E1 consisting of a drive pulse P7□ with a pulse width t and a high-frequency pulse f generated for a time t before the first pulse train E1, and a second pulse train E2 which is obtained by inverting the level of this pulse train.

Further, the pulse train P 1 is obtained by shifting the phase of the pulse train P7 by a time t.

On the other hand, the segment electrode S1 is selectively supplied with four types of selected pulse trains P-Pe, each consisting of pulses with a duty of 1/2 and a period of time 4t, shifted by 1/4 period Ml. be. The voltage of this pulse train is the same as that of pulse trains P 1 and P 2 .

First, by supplying the pulse train P3, the liquid crystal display element A1.
Voltages V and Vto are applied to A, respectively, and both become non-displayed.

Next, by supplying the pulse train P4, the liquid crystal display element A
, A is applied with a voltage v V 1 2
11' and 12, and are displayed and hidden, respectively.

Further, by supplying the pulse train P5, the liquid crystal display element A
, A are each applied with a voltage v v 1 2
13' and 14, and both are displayed.

Then, by supplying the pulse train P6, the liquid crystal display element At,
A2 has a voltage V15. Vie is applied to hide and display, respectively.

[Effects of the Invention] According to the present invention, only one pulse voltage is required to be supplied to the common electrode and the segment electrodes, so a step-up circuit or a step-down circuit is not required, and an external capacitor is also not required, and the circuit configuration can be simplified. It can be extremely simplified.

Furthermore, external capacitor pads are not required, which is effective in reducing the chip area of the integrated circuit.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing an example of the voltage waveform used in the driving method of the present invention, FIG. 2 is a front view showing an example of the common electrode,
Fig. 3 is a front view showing an example of segment electrodes, Fig. 4 is a front view showing a liquid crystal display element constructed by the electrodes shown in Figs. 2 and 3, and Fig. 5 is a front view showing an example of a segment electrode. FIG. 3 is a waveform diagram showing voltage waveforms that are c, -c3...Common electrode 81-S4...Segment 7u pole 81-A7...Liquid crystal display element El...First pulse train E2...Second pulse train PI3...Drive pulse fl...High frequency pulse P to P6...Selected pulse train or more

Claims (1)

[Claims] Two liquid crystal display elements are constituted by two common electrodes and segment electrodes facing each common electrode with a liquid crystal interposed therebetween, and one common electrode is provided with a driving pulse having a pulse width t. A first pulse train consisting of a high frequency pulse of the same voltage as the driving pulse occurring for a time t before or after this driving pulse, and a second pulse train formed by inverting the level of this first pulse train are alternately supplied. The first pulse train and the second pulse train are supplied to the other common electrode with a phase shift of time t from the one common electrode, and each segment electrode is supplied with the same voltage as the driving pulse. And the period is 4t, and the duty is 1/
A liquid crystal display device characterized in that it selectively supplies four types of selection pulse trains consisting of two pulses and whose phases are shifted by 1/4 period, and selectively displays and non-displays each of the liquid crystal display devices. Driving method.